Not Applicable.
Not Applicable.
1. Field of the Invention
The present invention relates to devices for handling coiled tubing for oil drilling operations. More particularly, the present invention relates to reels that have a capacity to hold extended lengths of coiled tubing. Still more particularly, the present invention relates to sectional transportable reels that have a capacity to hold extended lengths of coiled tubing.
2. Description of the Related Art
Coiled tubing, as currently deployed in the oilfield industry, generally includes small diameter cylindrical tubing made of metal or composites that have a relatively thin cross sectional thickness. Coiled tubing is typically much more flexible and much lighter than conventional drill string. These characteristics of coiled tubing have led to its use in various well operations. Coiled tubing is introduced into the oil or gas well bore through wellhead control equipment to perform various tasks during the exploration, drilling, production, and workover of a well. For example, coiled tubing is routinely utilized to inject gas or other fluids into the well bore, inflate or activate bridges and packers, transport well logging tools downhole, perform remedial cementing and clean-out operations in the bore, and to deliver drilling tools downhole. The flexible, lightweight nature of coiled tubing makes it particularly useful in deviated well bores.
Typically, coiled tubing is introduced into the oil or gas well bore through wellhead control equipment. A conventional handling system for coiled tubing can include a reel assembly, a gooseneck, and a tubing injector head. The reel assembly includes a rotating reel for storing coiled tubing, a cradle for supporting the reel, a drive motor, and a rotary coupling. During operation, the tubing injector head draws coiled tubing stored on the reel and injects the coiled tubing into a wellhead. The drive motor rotates the reel to pay out the coiled tubing and the gooseneck directs the coil tubing into the injector head. Often, fluids are pumped through the coiled tubing during operations. The rotary coupling provides an interface between the reel assembly and to a fluid line from a pump. Such arrangements and equipment for coiled tubing are well known in the art.
While prior art coiled tubing handling systems are satisfactory for coiled tubing made of metals such as steel, these systems do not accommodate the relatively long lengths of drill or working strings achievable with coiled tubing made of composites. Such extended lengths of composite coiled tubing strings are possible because composite coiled tubing is significantly lighter than steel coiled tubing. In fact, composite coiled tubing can be manufactured to have neutral buoyancy in drilling mud. With composite coiled tubing effectively floating in the drilling mud, downhole tools, such as tractors, need only overcome frictional forces in order to tow the composite coiled tubing through a well bore. This characteristic of composites markedly increases the operational reach of composite coiled tubing. Thus, composite coiled tubing can allow well completions to depths of 20,000 feet or more, depths previously not easily achieved by other methods.
Moreover, composites are highly resistant to fatigue failure caused by xe2x80x9cbending events,xe2x80x9d a mode of failure that is often a concern with steel coiled tubing. At least three bending events may occur before newly manufactured coiled tubing enters a well bore: unbending when the coiled tubing is first unspooled from the reel, bending when travelling over a gooseneck, and unbending upon entry into an injector. Such accumulation of bending events can seriously undermine the integrity of steel coiled tubing and pose a threat to personnel and rig operations. Accordingly, steel coiled tubing is usually retired from service after only a few trips into a well bore. However, composite coiled tubing is largely unaffected by such bending events and can remain in service for a much longer period of time.
Hence, systems utilizing composite coiled tubing can be safely and cost-effectively used to drill and explore deeper and longer oil wells than previously possible with conventional drilling systems. Moreover, completed but unproductive wells may be reworked to improve hydrocarbon recovery. Thus, composite coiled tubing systems can allow drilling operations into territories that have been inaccessible in the past and thereby further maximize recovery of fossil fuels.
However, these dramatic improvements in drilling operations require handling systems that can efficiently and cost-effectively deploy extended lengths of composite coiled tubing. In prior art coiled tubing handling systems, the reel assembly is generally the largest single component of the coiled tubing unit. The size of the reel assembly is often indirectly limited by various governmental codes and regulations. For example, on many domestic highway routes, additional fees are levied on tractor-trailer combinations that exceed a specified weight or size limitation. Further, because offshore platform space is at a premium, many drilling companies place strict requirements on the amount and size of equipment permitted on the rig at any given time. The size and load carrying limits of available barges or transport ships may also limit the physical size of the reel.
Nonetheless, a reel having a large storage capacity provides operational efficiencies. For example, two reels storing 12,000 feet of coiled tubing each can be deployed more efficiently than three reels storing 8,000 feet each. One reason for this efficiency is that a two reel configuration eliminates a reel change-out. That is, by carrying longer lengths at one time, large coiled tubing reels benefit drilling companies because they reduce the number of work stoppages required to insert a new reel of tubing into the work string. Because rig time is very expensive, it is often cost-effective to minimize the elapsed time for tubing deployment.
For these reasons, a coiled tubing system that both maximizes the length of tubing that can be deployed and minimizes the physical size of the unit is desired. Because composite coiled tubing can be deployed in lengths vastly greater than has been possible with steel coiled tubing, there is a need for a transportable reel that can store large quantities of coiled tubing.
In summary, while oil and gas recovery operations could greatly benefit from coil handling systems capable of handling long lengths of coiled tubing, the prior art does not disclose such handling systems.
The present invention overcomes the deficiencies of the prior art by including the design of a reel assembly that can be disassembled for transportation. Such a reel assembly may be deployed more efficiently than prior art designs. One benefit of this design is that the empty reel assemblies can be removed from the coiled tubing platform without disturbing the operation of the remaining reel assemblies in order to provide room on the platform for the remaining reel assemblies to operate without obstruction. This design allows empty reels to be packaged and shipped in a manner that is more efficient than what was possible under the limitations of the prior art.
Other objects and advantages of the present invention will be apparent in the following description.